//! Tracking and managing windows.

use std::{
    cmp::{max, min, Ordering},
    mem,
};

use crate::{
    buttons,
    config::BORDER_WIDTH,
    conn_info::Connection,
    debug,
    error::{Error, Result},
    WM,
};
use xcb::{
    x::{
        self, ChangeProperty, CloseDown, ConfigWindow, ConfigWindowMask, ConfigureNotifyEvent,
        ConfigureRequestEvent, ConfigureWindow, DeleteProperty, DestroyNotifyEvent, Drawable,
        EventMask, GetGeometry, GetWindowAttributes, InputFocus, KillClient, MapRequestEvent,
        PropMode, SetCloseDownMode, SetInputFocus, UnmapNotifyEvent, Window,
    },
    xinerama, BaseEvent, Extension, Xid,
};

pub use client::*;
pub use hints::*;
pub use monitors::*;

#[doc(hidden)]
mod client;

#[doc(hidden)]
mod hints;

#[doc(hidden)]
mod monitors;

mod tile;

/// The tag a client has, similar to a workspace in most WMs.
pub type Tag = u8;

pub type MonitorIdx = usize;
pub type ClientIdx = usize;

impl WM<'_> {
    /// Perform configure requests if we're happy with them, or they're for an unmanaged window.
    pub(crate) fn handle_configure_request(&mut self, e: &ConfigureRequestEvent) {
        if let Some(c) = self.clients.find_client_mut(e.window()) {
            // Always allow setting border width
            if c.floating() {
                c.set_geom_from(&self.conn, e);
            } else if e.value_mask().contains(ConfigWindowMask::BORDER_WIDTH) {
                c.set_geom(
                    &self.conn,
                    c.x(),
                    c.y(),
                    c.height(),
                    c.width(),
                    e.border_width(),
                );
            }

            c.configure_notify(&self.conn);
        } else {
            // Configure it as requested, and sort the rest when we actually map the window
            // According to spec, we should check the property mask and only set properties that are specified, setting defaults
            // for other ones.
            // Unfortunately, some clients (such as Audacity) will not set the mask correctly.
            // So instead we just use all the properties, and the ones that can be invalid (width, height > 0) we clamp.
            self.conn.send_request(&ConfigureWindow {
                window: e.window(),
                value_list: &[
                    ConfigWindow::X(e.x().into()),
                    ConfigWindow::Y(e.y().into()),
                    ConfigWindow::Width(max(e.width().into(), 1)),
                    ConfigWindow::Height(max(e.height().into(), 1)),
                    ConfigWindow::BorderWidth(e.border_width().into()),
                    ConfigWindow::StackMode(e.stack_mode()),
                ],
            });
        }
    }

    /// Update our monitor geometry if the root window is reconfigured
    pub(crate) fn handle_configure_notify(&mut self, e: &ConfigureNotifyEvent) -> Result<()> {
        if e.window() == self.conn.root() {
            self.clients.update_geometry(&self.conn)?;
        }
        Ok(())
    }

    /// Removing destroyed windows from the client list and rearrange.
    pub(crate) fn handle_destroy_notify(&mut self, e: &DestroyNotifyEvent) {
        // destroynotify gets fired twice: one with event = e.window(), and one with event = root
        // so only listen to the second one
        if e.event() == self.conn.root() {
            self.clients.unmanage_destroyed(&self.conn, e.window());
        }
    }

    /// Map a window, starting to manage it if needed.
    pub(crate) fn handle_map_request(&mut self, e: &MapRequestEvent) -> Result<()> {
        // Ignore already managed windows
        if self.clients.find_client_mut(e.window()).is_some() {
            return Ok(());
        }

        let attrs = self.conn.wait_for_reply(
            self.conn
                .send_request(&GetWindowAttributes { window: e.window() }),
        )?;
        if attrs.override_redirect() {
            // Something special, or us doing actual mapping. Don't manage it just let it do its thing.
            return Ok(());
        }

        // Start managing, and map window
        self.clients.manage(&self.conn, e.window());

        Ok(())
    }

    /// When a window is unmapped, update its state.
    pub(crate) fn handle_unmap_notify(&mut self, e: &UnmapNotifyEvent) {
        if !e.is_from_send_event() {
            if let Some(c) = self.clients.find_client_mut(e.window()) {
                let cookie = c.set_withdrawn(&self.conn, true);
                // The above may fail if the window has already been destroyed - just discard the error here.
                let _ = self.conn.check_request(cookie);
            }

            if self
                .clients
                .focused()
                .is_some_and(|c| c.window() == e.window())
            {
                self.clients.unfocus_destroyed();
            }
        }
    }
}

/// Holds state related to the window manager's clients
/// This contains a list of clients per monitor, alongside info on that monitor's screen size.
pub struct ClientState {
    /// The current arranging function.
    /// This function is expected to ensure that all clients are the correct size, reconfigure them if needed, and map/unmap as needed.
    arrange: &'static dyn Fn(&Connection<'_>, &mut [Client], &MonitorInfo),

    /// Clients attached to that monitor
    pub clients: Vec<Client>,

    /// Information for each monitor.
    mons: Vec<MonitorInfo>,

    /// Index of the currently focused client
    focused_client: Option<ClientIdx>,
}

impl ClientState {
    /// Start managing the given window, adding it to the client list and ensuring its configuration is valid.
    pub fn manage(&mut self, conn: &Connection<'_>, window: Window) {
        let mut tag = self.focused_mon().focused_tag.create_tag();
        let mut floating = false;
        if let Some(parent) = hints::transient_for(conn, window) {
            floating = true;
            if let Some(c) = self.find_client_mut(parent) {
                tag = c.tag;
            }
        }
        let is_visible = self.focused_mon().focused_tag.matches(tag);

        let new_idx = self.clients.len();
        self.clients.push(Client::new(window, tag));
        let Ok(geom) = conn.wait_for_reply(conn.send_request(&GetGeometry {
            drawable: Drawable::Window(window),
        })) else {
            return; // window stopped existing, so we can't manage it
        };

        let mon_geom = self.focused_mon().screen_info;

        let c = &mut self.clients[new_idx];
        #[allow(clippy::cast_sign_loss)]
        c.set_geom(
            conn,
            geom.x(),
            geom.y(),
            min(geom.width(), mon_geom.width.saturating_sub(geom.x() as u16)),
            min(
                geom.height(),
                mon_geom.height.saturating_sub(geom.y() as u16),
            ),
            BORDER_WIDTH,
        );
        c.set_border(conn, conn.colours.border_normal());
        if floating {
            c.set_floating(conn);
        }

        c.sync_hints(conn, true);
        c.apply_geometry_hints(conn, &mon_geom);
        c.set_event_mask(
            conn,
            EventMask::ENTER_WINDOW
                | EventMask::FOCUS_CHANGE
                | EventMask::PROPERTY_CHANGE
                | EventMask::STRUCTURE_NOTIFY
                | EventMask::BUTTON_PRESS
                | EventMask::KEY_PRESS,
        );

        // Add to net_client_list
        conn.send_request(&ChangeProperty {
            mode: xcb::x::PropMode::Append,
            window: conn.root(),
            property: conn.atoms.net_client_list,
            r#type: x::ATOM_WINDOW,
            data: &[window],
        });

        if is_visible {
            c.ensure_mapped(conn);
            self.rearrange(conn);
            self.refocus(conn, self.clients.len() - 1);
        }
    }

    /// Stop managing the given destroyed window
    pub fn unmanage_destroyed(&mut self, conn: &Connection<'_>, window: Window) {
        let Some(i) = self.find_client_pos(window) else {
            return;
        };
        let focused_mon = self.focused_mon().screen_info;

        self.clients.remove(i);

        self.focused_client = self.focused_client.and_then(|f| match f.cmp(&i) {
            Ordering::Less => Some(f),
            Ordering::Greater => Some(f - 1),
            Ordering::Equal => None,
        });
        if self.focused_client.is_none() {
            if let Some(i) = self
                .clients
                .iter()
                .position(|c| focused_mon.contains(c.x(), c.y()))
            {
                self.refocus(conn, i);
            }
        }

        self.rearrange(conn);
    }

    /// Refocus on the client with the given co-ordinates, setting X11 properties as required.
    /// If the given index is invalid, focus on the root instead.
    pub fn refocus(&mut self, conn: &Connection<'_>, i: ClientIdx) {
        self.unfocus(conn);
        if self.set_focused(i).is_some() {
            let mon_idx = self.client_mon_idx(i);
            let tag = self.client(i).tag;
            if !self.mons[mon_idx].focused_tag.matches(tag) {
                self.set_mon_tag_focus(conn, mon_idx, TagFocus::Tag(tag));
            }

            let new = self.client_mut(i);
            new.set_border(conn, conn.colours.border_focused());
            new.sync_hints(conn, true);

            buttons::grab(conn, new.window(), true);
            if !new.never_focus() {
                conn.send_request(&SetInputFocus {
                    revert_to: InputFocus::PointerRoot,
                    focus: new.window(),
                    time: x::CURRENT_TIME,
                });
                conn.send_request(&ChangeProperty {
                    window: conn.root(),
                    mode: PropMode::Replace,
                    property: conn.atoms.net_active_window,
                    r#type: x::ATOM_WINDOW,
                    data: &[new.window()],
                });
                conn.send_event(new.window(), conn.atoms.wm_take_focus);
            }
        } else {
            conn.send_request(&SetInputFocus {
                revert_to: InputFocus::PointerRoot,
                focus: conn.root(),
                time: x::CURRENT_TIME,
            });
            conn.send_request(&DeleteProperty {
                window: conn.root(),
                property: conn.atoms.net_active_window,
            });
        }
    }

    /// Unfocus the currently focused window, if it exists.
    pub fn unfocus(&mut self, conn: &Connection<'_>) {
        if let Some(old) = self.focused_mut() {
            old.set_border(conn, conn.colours.border_normal());
            buttons::grab(conn, old.window(), false);
        }
        self.focused_client = None;
    }

    /// Unfocus the currently focused window, if it exists, without doing any of the X11 parts.
    /// This is used when a focused window is destroyed or unmapped
    pub fn unfocus_destroyed(&mut self) {
        self.focused_client = None;
    }

    /// Go to the next or previous window in the current monitor, looping around if needed
    pub fn change_focus(&mut self, conn: &Connection<'_>, increase: bool) {
        if self.clients.is_empty() {
            return;
        }

        let tag_focus = self.focused_mon().focused_tag;
        let curr_focused = self.focused_client.unwrap_or(0);
        let look_through = self
            .clients
            .iter()
            .enumerate()
            .filter(|(_, c)| tag_focus.matches(c.tag))
            .filter(|(_, c)| self.focused_mon().screen_info.contains(c.x(), c.y()))
            .map(|(i, _)| i);

        let new_idx = if increase {
            look_through
                .cycle()
                .skip_while(|i| *i != curr_focused)
                .nth(1)
                .unwrap_or(0)
        } else {
            look_through
                .rev()
                .cycle()
                .skip_while(|i| *i != curr_focused)
                .nth(1)
                .unwrap_or(0)
        };

        self.refocus(conn, new_idx);
    }

    /// Shift the focused client up (increase = false) or down (increase = true) the client list
    pub fn shift_focused_client(&mut self, conn: &Connection<'_>, increase: bool) {
        // We always want to place it after/before the next/previous one on the focused tag
        let Some(target) = self.focused_client else {
            return;
        };
        let mon_idx = self.client_mon_idx(target);
        let tag_focus = self.mons[mon_idx].focused_tag;
        let look_through = self
            .clients
            .iter()
            .enumerate()
            .filter(|(_, c)| tag_focus.matches(c.tag))
            .filter(|(_, c)| c.tiled())
            .map(|(i, _)| i);

        let new_idx = if increase {
            look_through
                .cycle()
                .skip_while(|i| *i != target)
                .nth(1)
                .unwrap_or(0)
        } else {
            look_through
                .rev()
                .cycle()
                .skip_while(|i| *i != target)
                .nth(1)
                .unwrap_or(0)
        };

        // Need to do split it so that the borrow checker is happy
        match new_idx.cmp(&target) {
            Ordering::Less => {
                let (before, after) = self.clients.split_at_mut(target);
                mem::swap(&mut before[new_idx], &mut after[0]);
            }
            Ordering::Greater => {
                let (before, after) = self.clients.split_at_mut(new_idx);
                mem::swap(&mut before[target], &mut after[0]);
            }
            Ordering::Equal => return,
        }

        self.focused_client = Some(new_idx); // Doesn't need any actual X operations done
        self.rearrange_mon(conn, mon_idx);
    }

    /// Shift the focused client to the top of the stack
    pub fn shift_focused_to_top(&mut self, conn: &Connection<'_>) {
        if self.clients.len() == 1 {
            return; // Already at the top
        }

        let Some(target) = self.focused_client else {
            return;
        };

        // Need to do split it so that the borrow checker is happy
        let (before, after) = self.clients.split_at_mut(1);
        mem::swap(&mut before[0], &mut after[target - 1]);

        self.focused_client = Some(0); // Doesn't need any actual X operations done
        self.rearrange_mon(conn, self.focused_mon_idx());
    }

    /// Toggle whether the client with the given position is floating
    pub fn toggle_floating(&mut self, conn: &Connection<'_>, pos: ClientIdx) {
        let c = &mut self.clients[pos];
        if c.tiled() {
            c.set_floating(conn);
        } else {
            c.set_tiled(conn);
        }

        self.rearrange_mon(conn, self.client_mon_idx(pos));
    }

    /// Toggle whether the client with the given position is fullscreen
    pub fn toggle_fullscreen(&mut self, conn: &Connection<'_>, pos: ClientIdx) {
        let mon = self.client_mon_idx(pos);
        let mon_info = &self.mons[mon];
        let c = &mut self.clients[pos];
        if c.tiled() {
            c.set_fullscreen(conn, &mon_info.screen_info);
        } else {
            c.set_tiled(conn);
        }

        self.rearrange_mon(conn, mon);
    }

    /// Set the focused tag for the given monitor
    pub fn set_mon_tag_focus(
        &mut self,
        conn: &Connection<'_>,
        mon: MonitorIdx,
        tag_focus: TagFocus,
    ) {
        // Hide windows from currently focused tag filter
        let mon_info = &self.mons[mon];
        let curr_focus = mon_info.focused_tag;
        self.clients
            .iter_mut()
            .filter(|c| curr_focus.matches(c.tag))
            .filter(|c| mon_info.screen_info.contains(c.x(), c.y()))
            .for_each(|c| c.ensure_unmapped(conn));

        debug!("setting tag focus to {:?} on mon {}", tag_focus, mon);
        self.mons[mon].last_focused_tag = curr_focus;
        self.mons[mon].focused_tag = tag_focus;

        self.rearrange_mon(conn, mon);
        self.unfocus(conn);
        self.focused_client = self.clients.iter().position(|c| tag_focus.matches(c.tag));
    }

    /// Set the given monitor's focused tag to its previous value
    pub fn mon_prev_tag_focus(&mut self, conn: &Connection<'_>, mon: MonitorIdx) {
        self.set_mon_tag_focus(conn, mon, self.mons[mon].last_focused_tag);
    }

    /// Set the tag for the given client
    pub fn set_client_tag(&mut self, conn: &Connection<'_>, pos: ClientIdx, tag: Tag) {
        let c = self.client_mut(pos);
        if c.tag == tag {
            return;
        }

        debug!("moving client with window {:?} to tag {}", c.window(), tag);
        c.tag = tag;
        c.ensure_unmapped(conn);
        self.unfocus(conn);
        self.rearrange_mon(conn, self.client_mon_idx(pos));
    }

    /// Update the recorded monitors and monitor sizes, retiling if necessary.
    pub fn update_geometry(&mut self, conn: &Connection<'_>) -> Result<()> {
        let mut dirty = false;
        if conn.active_extensions().any(|e| e == Extension::Xinerama) {
            let reply = conn.wait_for_reply(conn.send_request(&xinerama::QueryScreens {}))?;

            // Monitor removed, move its clients away
            if reply.screen_info().len() > self.mons.len() {
                dirty = true;
                self.truncate_screens(reply.screen_info().len());
            }

            // Update screen info & add new client lists if needed
            for (i, monitor) in reply.screen_info().iter().enumerate() {
                dirty |= self.set_monitor_geometry(i, (*monitor).into());
            }
        } else {
            // Only one screen
            if self.mons.len() > 1 {
                dirty = true;
                self.truncate_screens(1);
            }

            // TODO: it looks like this won't actually update when the screen size changes?
            let setup = conn.get_setup();
            let screen = setup
                .roots()
                .nth(conn.screen_num())
                .ok_or(Error::NoSuchScreen)?;

            dirty |= self.set_monitor_geometry(
                0,
                MonitorGeometry {
                    x_org: 0,
                    y_org: 0,
                    width: screen.width_in_pixels(),
                    height: screen.height_in_pixels(),
                },
            );
        }

        if dirty {
            self.rearrange(conn);
        }
        Ok(())
    }

    /// Set the new amount of screens
    fn truncate_screens(&mut self, new_size: usize) {
        match new_size.cmp(&self.mons.len()) {
            Ordering::Greater => {
                for _ in 0..new_size - self.mons.len() {
                    self.mons.push(MonitorInfo::default());
                }
            }
            Ordering::Less => {
                self.mons.drain(new_size - self.mons.len()..self.mons.len());
            }
            Ordering::Equal => (),
        }
    }

    /// Set the given screen's geometry, resizing the monitor list if necessary.
    /// Returns true if the new info is different from the old one.
    fn set_monitor_geometry(&mut self, i: MonitorIdx, info: MonitorGeometry) -> bool {
        while i >= self.mons.len() {
            self.mons.push(MonitorInfo::default());
        }
        let dirty = self.mons[i].screen_info != info;
        self.mons[i].screen_info = info;

        dirty
    }

    /// Find the [`Client`] corresponding to the given window
    pub fn find_client_mut(&mut self, window: Window) -> Option<&mut Client> {
        let i = self.find_client_pos(window)?;
        Some(&mut self.clients[i])
    }

    /// Find the position of the client with the given window, returning an index
    pub fn find_client_pos(&self, window: Window) -> Option<ClientIdx> {
        self.clients.iter().position(|c| c.window() == window)
    }

    /// Get the index of the currently focused client, if it exists
    pub const fn focused_pos(&self) -> Option<ClientIdx> {
        self.focused_client
    }

    /// Get a reference to the currently focused client, if it exists.
    pub fn focused(&self) -> Option<&Client> {
        self.focused_client.map(|i| self.client(i))
    }

    /// Get a mutable reference to the currently focused client, if it exists.
    pub fn focused_mut(&mut self) -> Option<&mut Client> {
        self.focused_client.map(|i| self.client_mut(i))
    }

    pub fn is_focused(&self, e: Window) -> bool {
        self.focused().is_some_and(|c| c.window() == e)
    }

    /// Set the currently focused client, returning a mutable reference to the client.
    pub fn set_focused(&mut self, mut i: ClientIdx) -> Option<&mut Client> {
        if self.clients.is_empty() {
            return None;
        }

        if i >= self.clients.len() {
            i = self.clients.len() - 1;
        }

        self.focused_client = Some(i);
        Some(&mut self.clients[i])
    }

    /// Get a reference to the client at the given index
    pub fn client(&self, i: ClientIdx) -> &Client {
        &self.clients[i]
    }

    /// Get a mutable reference to the client at the given index
    pub fn client_mut(&mut self, i: ClientIdx) -> &mut Client {
        &mut self.clients[i]
    }

    /// Rearrange all clients, reconfiguring them as needed.
    pub fn rearrange(&mut self, conn: &Connection<'_>) {
        for mon in 0..self.mons.len() {
            self.rearrange_mon(conn, mon);
        }
    }

    /// Rearrange a specific monitor
    pub fn rearrange_mon(&mut self, conn: &Connection<'_>, mon: MonitorIdx) {
        (self.arrange)(conn, &mut self.clients, &self.mons[mon]);
    }

    /// Get the index of the currently focused monitor
    pub fn focused_mon_idx(&self) -> MonitorIdx {
        self.focused_client.map_or(0, |i| self.client_mon_idx(i))
    }

    /// Get the info for the currently focused monitor
    pub fn focused_mon(&self) -> &MonitorInfo {
        &self.mons[self.focused_mon_idx()]
    }

    /// Get the monitor info for the client with the given index
    pub fn client_mon_idx(&self, pos: ClientIdx) -> MonitorIdx {
        let c = self.client(pos);
        self.mons
            .iter()
            .position(|m| m.screen_info.contains(c.x(), c.y()))
            .unwrap_or_else(|| self.mons.len() - 1)
    }

    /// Get the monitor info for the client with the given index
    pub fn client_mon(&self, pos: ClientIdx) -> &MonitorInfo {
        &self.mons[self.client_mon_idx(pos)]
    }

    pub fn kill_client(&self, conn: &Connection, pos: usize) {
        let c = self.client(pos);
        // Modern clients respond to the WM_DELETE event
        if !conn.send_event(c.window(), conn.atoms.wm_delete) {
            // Fallback to the old fashioned way

            // Using checked requests so we can ignore errors here without waiting for them to go to
            // the event loop
            let cookie1 = conn.send_request_checked(&SetCloseDownMode {
                mode: CloseDown::DestroyAll,
            });
            let cookie2 = conn.send_request_checked(&KillClient {
                resource: c.window().resource_id(),
            });

            let _ = conn.check_request(cookie1);
            let _ = conn.check_request(cookie2);
        }
    }
}

impl Default for ClientState {
    fn default() -> Self {
        Self {
            arrange: &tile::tile,
            mons: vec![],
            clients: vec![],
            focused_client: None,
        }
    }
}

impl std::fmt::Debug for ClientState {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ClientState")
            .field("focused_client", &self.focused_client)
            .field("mons", &self.mons)
            .field("clients", &self.clients)
            .finish_non_exhaustive()
    }
}